This invention relates to automatic non-contact measurements of optical properties of optical objects, particularly, to mapping optical objects.
The present invention particularly refers to a method and system for mapping an ophthalmic element, where optical properties of the element such as its optical power are measured simultaneously along the element""s entire surface. U.S. Pat. No. 4,810,895, U.S. Pat. No. 5,825,476, and U.S. Pat. No. 5,896,194 illustrate different kinds of such methods and systems.
U.S. Pat. No. 4,810,895 discloses a method and apparatus for moire ray deflection mapping, where properties of an object are determined by producing a diverging beam of direct light from a point radiation source, passing this beam through a first optical system including the object to be examined, which system retraces the light in the form of a converging beam of reflected light from the examined object back towards the point source. The converging beam of reflected light is intercepted before reaching the point source and is passed through a second optical system which collimates the beam of reflected light. The collimated beam is then directed through first and second gratings at a preselected angular orientation with respect to each other to produce moire fringe patterns providing an indication of the properties of the examined object.
U.S. Pat. No. 5,825,476 discloses an apparatus for mapping an optical object, including a light source directing a light beam towards the optical object, an array of microlenses which divide the light beam passed through the optical object into a plurality of light beams at least some of which differ from each other, and form on a diffusive screen a corresponding plurality of images of the light source, a camera for recording these images and a computer for processing the multiple images and comparing them with a reference pattern.
U.S. Pat. No. 5,896,194 discloses an apparatus which includes a first light source for generating a lens-characteristic measuring light beam, a second light source for generating a position specifying light beam, a pattern plate with lens-characteristic measuring patterns and position specifying patterns, on which the beams from the light sources are projected through an inspected optical object to receive images of the patterns on a diffusive screen. The received images are analyzed, and the lens-characteristic mapping display of the inspected lens is performed.
It is the object of the present invention to provide a novel method and system for automatic non-contact measuring optical properties of an optical object.
In accordance with one aspect of the present invention, there is provided a method for automatic non-contact measuring optical properties of an optical object by means of a system comprising a light source, a reference pattern, an imaging and detecting means, at least the reference pattern and the imaging and detecting means being disposed on an optical axis of the system, and an image processing means.
The method of the present invention comprising the steps of:
(a) disposing said optical object between said reference pattern and said imaging and detecting means coaxially therewith;
(b) directing to said pattern an illuminating light from said light source in such a manner as to produce a plurality of illuminating light beams outcoming from each point of the pattern at different angles;
(c) imaging said pattern through said optical object by means of imaging beams each of which is conjugate with only one of said illuminating beams and detecting the image, by said imaging and detecting means, and
(d) processing said image by said image processing means and producing a measurement output, preferably by comparing the image with an image of said pattern obtained by said imaging and detecting means in the absence of said optical object.
According to another aspect of the present invention, there is provided a system for automatic non-contact measuring optical properties of an optical object, comprising a light source, a reference pattern, an imaging and detecting means, at least the reference pattern and the imaging and detecting means being disposed on an optical axis of the system, a support for the optical object located between said reference pattern and said imaging and detecting means for disposing thereon the optical object coaxially with said pattern and said imaging and detecting means, said light source being capable of directing to said pattern an illuminating light in such a manner as to produce a plurality of illuminating light beams outcoming from each point of the pattern at different angles, said imaging and detecting means being capable of obtaining an image of said pattern through said optical object so that each imaging beam is conjugate with only one of said illuminating beams, and of recording said image, and an image processing means for processing said image and producing a measurement output.
In the method and system according to the present invention, the pattern and the light source illuminating it are so designed as to ensure that the light outcoming from the illuminated reference pattern is scattered, whereby said plurality of illuminating beams outcoming from each point of the pattern is provided. The conjugation of each imaging beam with only one of said plurality of illuminating beams is achieved by said imaging and detecting means including a detector camera with a camera lens whose entrance pupil allows only an extremely narrow light beam to pass therethrough. Thereby, the detector camera in fact chooses from the plurality of illuminating beams only those whose angles of incidence on the inspected optical object suit the setup of the imaging and detecting means, and uses these beams for forming the image of the reference pattern.
To provide the scattered light outcoming from the reference pattern, the light source may be in the form of a diffusive illuminator or it may be an arbitrary monochromatic light source whose light is specifically diffused prior to its impinging the reference pattern. In this case the reference pattern may be formed on transparent material such as mineral glass or it may be rather formed on a plate with a coating providing a total internal reflection. Alternatively, the pattern itself may be made of, or formed on, a diffusing (scattering) material (reflecting or transmitting) such as milky glass, ground glass or paper.
The reference pattern is preferably in the form of a number of regularly arranged pattern elements having known dimensions and shapes and known mutual disposition. For example, these elements may be points, lines or circles, concentric circular and radial lines, staggered squares, regular grid and the like. The pattern may have highlighted origin lines. It may be designed as a black pattern on a bright background or white pattern on a dark background. It may be in the form of a plurality of openings or slits.
With the method and system of the present invention, the inspected optical object introduces, due to its refractive properties, deformation into dimensions, shapes and/or positions of the elements of the imaged pattern. Thus, spherical power leads to the magnification of the imaged pattern elements. Cylindrical optical power leads to their deformation with the direction of the deformation indicating to the orientation of the cylinder axis. Prismatic power leads to the parallel displacement of the elements of the pattern image relative to their reference position, with the direction of the displacement indicating to the orientation of the prism axis. Measurements of these deformations enable the calculation of the optical object""s refractive properties at any point and, if desired, their presentation in the form of a map of the optical object along its entire inspected area. The map may be a spherical optical power map, a cylindrical optical power map or a prismatic optical power map, the two latter maps being each accompanied by a corresponding vector field characterizing the direction of the respective cylinder or prism axes at different areas of the inspected optical object. Alternatively, the map may be in the form of a topographic map presenting point-to-point heights of the optical object""s inspected surface.